updates

pkg/agent/compaction_test.go

@@ -1,8 +1,11 @@
 package agent
 
 import (
+	"encoding/json"
 	"os"
 	"testing"
+
+	"ollie/pkg/backend"
 )
 
 type mockBackendForCompact struct {
@@ -38,7 +41,7 @@ func TestResolveCompactionModel_BackendDefault(t *testing.T) {
 	}{
 		{"anthropic", "claude-3-5-haiku-latest"},
 		{"openai", "gpt-4o-mini"},
-		{"openrouter", "gpt-4o-mini"},
+		{"openrouter", "deepseek-v4-flash"},
 		{"gemini", "gemini-2.0-flash"},
 		{"ollama", ""},
 	}
@@ -50,3 +53,61 @@ func TestResolveCompactionModel_BackendDefault(t *testing.T) {
 		}
 	}
 }
+
+func TestBuildCompactedHistory_OrphanedToolMessage(t *testing.T) {
+	// Simulate a history where the hot zone boundary (total - hotTailSize)
+	// lands on a tool message whose preceding assistant+tool_calls is outside
+	// the hot zone. Without the fix, this produces an orphaned tool message
+	// that causes OpenAI 400 errors.
+	var msgs []backend.Message
+
+	// Pad with enough messages so the boundary falls on the tool message.
+	// We need total - hotTailSize to land on the tool result.
+	// hotTailSize = 8, so we need the tool msg at index total-8.
+	// Build: 10 user/assistant pairs (20 msgs), then assistant+tool_calls, tool result, then 7 more messages.
+	for i := range 10 {
+		msgs = append(msgs,
+			backend.Message{Role: "user", Content: "q" + string(rune('0'+i))},
+			backend.Message{Role: "assistant", Content: "a" + string(rune('0'+i))},
+		)
+	}
+	// assistant with tool_calls at index 20
+	msgs = append(msgs, backend.Message{
+		Role:      "assistant",
+		ToolCalls: []backend.ToolCall{{ID: "call_orphan", Name: "test_tool", Arguments: json.RawMessage(`{}`)}},
+	})
+	// tool result at index 21 — this is where hotStart would land without the fix
+	msgs = append(msgs, backend.Message{
+		Role:       "tool",
+		Content:    "tool output",
+		ToolCallID: "call_orphan",
+	})
+	// 7 more messages to fill the rest of the hot zone (indices 22-28)
+	for i := range 3 {
+		msgs = append(msgs,
+			backend.Message{Role: "user", Content: "follow " + string(rune('0'+i))},
+			backend.Message{Role: "assistant", Content: "reply " + string(rune('0'+i))},
+		)
+	}
+	msgs = append(msgs, backend.Message{Role: "user", Content: "final"})
+	// total = 29, hotStart = 29 - 8 = 21 (the tool message)
+
+	ts := TaskState{Objective: "test"}
+	result := buildCompactedHistory(ts, msgs)
+
+	// Verify no tool message appears without a preceding assistant+tool_calls.
+	for i, m := range result {
+		if m.Role == "tool" {
+			if i == 0 {
+				t.Fatalf("result[0] is a tool message — no preceding assistant")
+			}
+			prev := result[i-1]
+			if prev.Role != "assistant" && prev.Role != "tool" {
+				t.Fatalf("result[%d] is tool but result[%d] is %q (want assistant or tool)", i, i-1, prev.Role)
+			}
+			if prev.Role == "assistant" && len(prev.ToolCalls) == 0 {
+				t.Fatalf("result[%d] is tool but preceding assistant has no tool_calls", i)
+			}
+		}
+	}
+}

pkg/agent/session.go

@@ -348,6 +348,16 @@ func buildCompactedHistory(ts TaskState, allMessages []backend.Message) []backen
 	if hotStart < 0 {
 		hotStart = 0
 	}
+
+	// If hotStart lands on a tool message, walk backward to include the
+	// preceding assistant message with tool_calls. Without this, the hot
+	// zone starts with an orphaned tool result which violates the OpenAI
+	// API constraint that tool messages must follow an assistant message
+	// containing the corresponding tool_calls.
+	for hotStart > 0 && allMessages[hotStart].Role == "tool" {
+		hotStart--
+	}
+
 	warmStart := hotStart - warmIndexSize
 	if warmStart < 0 {
 		warmStart = 0